Pumping plants for transferring liquid such as sewage from a "wet well" to the head works of a treatment station normally include some type of hydraulic surge protection means particularly directed towards eliminating or reducing water hammer. For example, where several large motor driven pumps are powered from electrical power bus lines for pumping the liquid through a fairly large capacity pipeline, should a power failure occur, the water column tends to separate in much the same manner as a series of freight cars pushed by a locomotive will separate if the driving locomotive slows or stops. Thus, if the pump pressure drops below vapor pressure, the water column in the pipeline can separate and results in severe water hammer.
The presently used surge protectors to avoid the foregoing problem may take many forms such as pneumatic surge chambers, pressurized stand pipes, one-way surge chambers, and so forth. These surge protectors are relatively bulky and massive and can increase substantially the cost of a pumping plant.
Another means for protecting against column separation would be to devise some system to keep the motor driven pumps operating after a power failure for a sufficient length of time to avoid column separation or at least reduce the column separation to a point where damaging water hammer is prevented. One manner of carrying out this concept would be to provide the motor driven pumps with fly wheels of sufficient inertia to maintain the pumps effectively in operation even should there be a power failure. The problem with attempting to use a fly wheel on the pump, however, is that most of the pumps particularly in large plants are of relatively low speed thereby limiting the amount of energy that can be stored in a fly wheel attached to the pump. Also, there are encountered problems in actually physically affixing the fly wheel to the pump.